The purposes of this research are (a) to study the effects of normal aging and certain dementia-producing illnesses on language-speech and cognitive functions, (b) to evaluate the potential of language tests for discriminating etiologically different dementias, and (c) to document through periodic assessment the dissolution of language-speech skills in etiologically different dementia patients. Normal elderly individuals who have no history of neurological disease are being compared to individuals who, as a result of neurological examination, have been diagnosed as having Alzheimer's disease (senile brain disease), Huntington's disease, Parkinson's disease, and multi-infarct dementia. Study participants are given the following five neuropsychological tests reputed sensitive to dementia and seven language tasks: Neuropsychological tests: 1) Mental Status Questionnaire; 2) Nonsense Syllable Learning Task; 3) Forward Digit Span (WAIS); 4) Block Design (WAIS); 5) Similarities (WAIS). Language Tasks: 1)Naming Task; 2) Peabody Picture Vocabulary Task; 3) Verbal Expression Test; 4) Story-retelling Test; 5) Sentence Correction Test; 6) Pragmatics Task; 7) Sentence Disambiguation Task.